Half to petee jeffeey



(No Model.)

J. MGG'OVERN.

GAISSON 0R CRIB.

No. 320,671. Patented June-Z3, 1885.

OgITNESSES mvnmon M W Y BY 7 ATTORMI N. PETERS. Fhowumo m her.Wuhington. D. c,

UNIT D STATES PATENT OFFICE.

JOHN MOGOVERN, OF MURPHYSBOROUGH, ILLINOIS, ASSIGNOB OF ONE- HALF TOPETER JEFFREY, OF SAME PLACE.

CAISSON OR CRIB.

SPECIPIOATIQN forming part of Letters Patent No. 320,671, dated June 23,1885.

Application filed August 9, 1884.

(No model.)

To all whom, it may concern:

Be it known that I, JOHN MoGovERN, of Murphysborough, in the county ofJackson and State of Illinois, have invented anew and useful Improvementin Gaissons or Cribs, of which the following is a full, clear, and exactdescription.

The object of my invention is to facilitate the work of sinking coalshafts and wells and excavating for bridge-foundation in groundsuch asmud or quicksand-wvhich breaks into the excavation before it can betimbered.

It consists in a caisson or crib constructed and arranged for being sunkin advance of the main work, as hereinafter described and claimed.

Reference is to be had tothe accompanying drawings, forming a part ofthis specification, in which similar letters of reference indicatecorresponding parts in both the figures.

Figure l is a vertical section representing a shaft in process ofconstruction with the caisson. Fig. 2 is a horizontal section.

The lower portion, A, of the crib is constructed of timber and of asizeinternally cor responding to the finished shaft. The lower portion isbeveled to asharp edge, a, and shod with iron, so that it may enter theground readily. The upper portion, B, of the caisson, formed ofboiler-iron, is bolted to the part A on the outside, and is of a lengthto extend some distance upward outside the permanent timbering O of theshaft, so as to prevent mud or sand from running into the excavatedspace at the bottom. At D, on the inside of part B, are ribs takingagainst the timbering O, to insure equal space all around for insertingthe timbers.

In using the caisson in the work of sinking a shaft it is graduallyforced down by jackscrews placed, as shown at E, betweenthe top of theportion A and the lower course of the permanent timbers. It will ofcourse be understood that in the soft ground in which the caisson is tobe used the resistance to the screws will be less at the point a than itis at thebase of timber O. In other words, the timbers G cannot, owingto the character of the ground, he raised when the screws are operated,and it follows, therefore, that the point a will be forced downward.After being driven far enough to give space for a course of timber, thescrews are removed, the material excavated enough to permit of the work,and the timbers then put in, after which the screws are again applied.The mud or sand is allowed to remain within the caisson up nearly to thetop of part A and only removed as necessary, so that the caisson shallbe held down to place.

By this mode of operating, shafts can be readily sunk in mud or shiftingground.

Having thus described my invention,[ claim as new and desireto secure byLetters Patent- The caisson or crib for use in sinking shafts,consisting of the timbered portion A, the extension B, ofboiler-iron,made large enough to inclose the permanent walls of the shaft, andthehorizontal ribs D, extending around the inner surface of the extensionB, substantially as set forth.

JOHN MOG OVERN.

\Vitnesses:

THOMAS WATsoN, WILLIAM R. DAVIDSON.

